In the midst of the worst economic crisis in a generation, Jeffrey Sachs insists that we need to focus on wiping out the most extreme poverty on the planet.

A. Well, it turns out that, given the way the economics of mobile phones work, it really makes sense for service providers to put up towers just about everywhere, even in very poor rural areas. The towers don’t cost all that much. It’s also possible to divide user charges into tiny amounts for a few seconds of phone time. In very poor communities, the phone companies have very cleverly set contracts or arrangements for subscribers that allow even extremely poor households to get at least a small bit of connectivity.

This means that mobile phones, without the need of foreign assistance, are reaching huge numbers of people. In African villages you now have at least a few phones around, and everybody knows who has them. If a mother is dying in childbirth and needs a truck or an ambulance, it’s now possible to provide emergency response in ways that were unimaginable just a few years ago.

Q. In terms of poverty and development challenges, doesn’t Afghanistan, now very much on the radar of the Obama administration, face issues similar to those in sub-Saharan Africa.

A. Afghanistan is one of the poorest countries in the world and has two of the biggest risk factors for impoverishment. One is that it’s a landlocked country. That means that it’s quite hard to be engaged in normal international trade—for example, in the manufacturing sector. Manufacturers like to invest right at a port on the coast of a continent.

The other major risk factor for Afghanistan is that it is very dry and drought-prone. This is a hungry, water-stressed part of the world, and water stress is a terrible burden on development because we use water to grow food. If we can’t grow enough food, people are hungry. When people are hungry, societies are unstable.

Q. What needs to be part of the administration’s overall strategy in Afghanistan?

A. There really are very serious security problems in Afghanistan. Still, we should not misunderstand the basic truth that as many troops as we put in, Afghanistan will not be stable unless we address—and help Afghanistan and its neighbors to address—the challenges of water, hunger, disease and illiteracy. Afghanistan needs transport and communication, a solution to its water crisis, investment in agriculture and investment in schools and training.

Q. Most Americans have never seen Afghanistan but presumably would like to help in some way. What can they do?

A. Well, I first would encourage everybody to learn and to read and understand about these challenges and to appreciate that there are hundreds of millions of people in desperate need where we have the capacity to help, and by helping, to make a safer world. So the first thing is make the commitment to be well-informed. Have an open mind and open eyes and ears about this.

Then there are many things that individuals have been doing and can do. I worked with a number of philanthropists in New York City and around the world to establish a nongovernmental organization, a not-for-profit called Millennium Promise. People who go to our website can learn a lot about our activities—for example, the way a contribution of $10 to enable a child to sleep under an antimalaria bed net can save lives. We find that the more people learn, the more they want to be involved.